The present disclosure relates to focus adjustment for camera lenses.
Generally, cameras accept visual light through a camera lens and capture that light on a recording surface—film, or as is now common, a digital sensor. In order to reproduce an object clearly, the object must be in focus. The focus level of the various objects in a camera viewfinder may be adjusted by changing the size of the camera lens aperture or by varying the distance between the camera lens and the recording surface.
For many premium cameras, such as high-end movie cameras, it is desirable that the focus be as precise as possible. Images from these cameras are often displayed in large formats, in which small errors in focus are readily apparent. In these contexts, even minor factors, like discrepancies in the mechanical tolerances at the lens mount, can throw off the focus of an image.
It is common practice to calibrate a lens's focus when it is first placed onto a camera with thin shims placed in a camera's lens mount at the base of the lens. The camera operator uses these shims, often made of paper, to make precise adjustments to the focal length, between the camera lens and sensor. In the case of a movie camera, this calibration process is laborious and time-consuming. Factors such as heat and repeated use of the shims introduce new variables, as they can change the thickness of the shim or camera components and alter the focal length between camera lens and sensor.
The time-consuming calibration process delays filming and therefore generates expense. New technology is desirable to simplify the lens calibration process.